Whirlpool spas are typically comprised of a molded, fiber reinforced plastic. shell which is seated in a cabinet. The shell contains water which is circulated through a filter and a heater by a filter pump. Typically, a spa will use a single, two speed pump motor. The filtering and heating function is usually accomplished with the pump motor in the low speed mode.
The high speed mode of the pump motor is typically engaged when the spa is in use and the occupants desire a vigorous circulation of water through the jets within the spa. Alternatively, an optional, two pump system can be had wherein the low speed filter pump function and the high speed jet pump function are segregated into two separate pump and piping systems.
An optional air blower is often associated with the spa for injecting air bubbles into the spa. The heater, filter pump, jet pump and blower are typically located in the cabinet, generally below and to one side of the spa shell. A heater thermostat and an automatic timer for the filter pump are also typically located inside the cabinet. Only the on/off controls for the jet pump and the air blower, and sometimes optional spa light controls, are located on the lip of the spa shell so that they are accessible by a person using the spa. Usually, one must open a door on the side of the spa cabinet and reach into the cabinet in order to access or to service the primary controls, the heater, the filter, the pump(s) and the blower.
This is a somewhat awkward and cumbersome procedure, especially with respect to operation of the automatic timer controls and mode selection switches, which must be accessed on a regular basis. It is also a particularly cumbersome procedure to service or maintain the filter, as one must do approximately every month.
In order to change or clean the filter element, a valve on each side of the filter must be closed to keep the water in the spa shell from draining out of the filter housing when it is opened to remove the filter element. Then, the water must be drained from the filter housing itself. The filter housing must be opened and the filter element is then removed and either replaced or cleaned.
Because the foregoing is such an awkward procedure, some spa manufacturers provide a filter which is mounted in the top corner of the spa shell itself and which can be removed from the top of the spa. The cover for the filter opening is located at the top of the spa, above the water line such that the filter element sits in a normally covered well-like opening. When the cover is removed, the user pulls the filter element directly up out of the filter housing.
One drawback to the corner placement of the filter is the restriction of the interior shape of the spa shell since approximately eight inches are required to locate the filter opening in the corner of the spa shell. Thus, the filter protrudes into the spa bathing area and eliminates certain space otherwise available for bathing.
Top mounted filters can be divided into two categories: filters that operate under pressure and filters that operate under a vacuum. Many manufacturers that provide top mounted filters prefer to use vacuum filter systems. Many manufacturers prefer vacuum filters, not because they are a better filtration system, but because water can be drawn through submerged cartridges without the need for a pressure vessel. Vacuum cartridges may be totally exposed, and thus provide a less expensive system which is easy to service. Because the centrifugal pumps commonly used in vacuum filtration systems do not create a high vacuum, a small amount of debris on a vacuum filter cartridge will substantially reduce the flow to the pump. As the filter media becomes clogged, the suction side of the pump begins to operate under an elevated vacuum, causing cavitation bubbles to form which erode the pump impeller. To minimize this problem, the filter cartridge must be cleaned frequently or cartridges with larger surface areas must be used, requiring even more space in the spa interior.
Some manufacturers use a top mounted pressure filtration system in their spas. Pressure filtration systems are superior to vacuum filtration systems in that they provide longer cycles between cleaning using less filter surface area. However, because pressure filtration systems operate under pressure, prior art cartridges are enclosed in a pressure vessel having a diameter of eight inches or more. Even though this dimension is smaller than that required by vacuum filtration systems, it still presents problems in designing efficient and ergonomic seating in the spa. Hence, accessibly mounting adequately sized filters in spas without sacrificing seating space has been difficult in prior known spas.